 /*******************************************************************************
  * Copyright (c) 2005, 2006 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  * IBM Corporation - initial API and implementation
  *******************************************************************************/
 package org.eclipse.ui.navigator;

 import org.eclipse.jface.viewers.IContentProvider;
 import org.eclipse.jface.viewers.StructuredViewer;
 import org.eclipse.ui.internal.navigator.NavigatorContentService;


 /**
  * Provides a factory pattern for creating {@link INavigatorContentService}s
  * for given viewer ids.
  *
  * <p>
  * Clients may supply the viewer in {@link #createContentService(String, StructuredViewer) }
  * or wait until the content provider is created by the service
  * and set on the viewer. When the content provider is set, the
  * viewer will call inputChanged(), and the content service
  * will update its managed viewer accordingly. Therefore, each
  * content service should be attached to at most one viewer.
  * </p>
  *
  * @since 3.2
  *
  */
 public final class NavigatorContentServiceFactory {
     
     /**
      * The singleton instance for creating NavigatorContentServices.
      */
     public static final NavigatorContentServiceFactory INSTANCE = new NavigatorContentServiceFactory();
     
     
     /**
      * Returns an instance of INavigatorContentService configured
      * for the given id. Instances are not shared for the same
      * viewerId.
      *
      * @param aViewerId The viewer id of interest
      * @return An instance of INavigatorContentService configured for the given id.
      */
     public INavigatorContentService createContentService(String aViewerId) {
         return createContentService(aViewerId, null);
     }
     
     /**
      * Returns an instance of INavigatorContentService configured
      * for the given id. Instances are not shared for the same
      * viewerId.
      *
      * @param aViewerId The viewer id of interest
      * @param aViewer The content service can use the given viewer to initialize content providers
      * @return An instance of INavigatorContentService configured for the given id.
      * @see IContentProvider#inputChanged(org.eclipse.jface.viewers.Viewer, Object, Object)
      */
     public INavigatorContentService createContentService(String aViewerId, StructuredViewer aViewer) {
         if(aViewer == null) {
             return new NavigatorContentService(aViewerId);
         }
         return new NavigatorContentService(aViewerId, aViewer);
     }

 }

